Researchers at the Highway Loss Data Institute, a leader in insurance analysis, released a study last week claiming that states with legalized recreational marijuana are seeing more car crashes than states still practicing prohibition. But while those researchers tried to ascribe their data to legalization and a possible increase in driving-while-stoned, a completely separate study in the American Journal of Public Health, also published last week, completely refutes those claims, saying that legal weed states have had no increase in car accidents or fatalities.

Analysts at the University of Texas-Austin looked at data from the US Fatality Analysis Reporting System to examine deaths by car accident in Colorado, Washington and eight control states that haven’t legalized cannabis. Additionally, the team looked at all available non-fatal crash data reported by those 10 states. In both instances, researchers found no correlation between legal cannabis and car accidents.

“We found no significant association between recreational marijuana legalization in Washington and Colorado and subsequent changes in motor vehicle fatality rates in the first three years after recreational marijuana legalization,” the study’s author concludes. “[W]e also found no association between recreational marijuana legalization and total crash rates when analyzing available state-reported nonfatal crash statistics.”

So while researchers at the Highway Loss Data Institute, who also looked at data from Washington and Colorado, used their findings to suggest lawmakers reconsider the safety of legalization, cannabis advocates are pointing to the University of Texas study to refute those claims. 

“These conclusions ought to be reassuring to lawmakers and those in the public who have concerns that regulating adult marijuana use may inadvertently jeopardize public safety. These results indicate that such fears have not come to fruition, and that such concerns ought not to unduly influence legislators or voters in other jurisdictions that are considering legalizing cannabis.” NORML Deputy Director Paul Armentano said about the University of Texas study.

And while it is possible that more drivers are reporting highway accidents in Washington and Colorado in the past few years, it would be a stretch to ascribe that increase to legal weed. What we do know, though, is that car crash fatality numbers, on both highways and residential roads, did not comparatively increase in the two legal weed states in the years since legalization. 

But still, cannabis has only been legal in Washington and Colorado for three years, and without more data it would be hard for either study to make any strong causation claims. What ending prohibition does allow, however, is more comprehensive research in the first place – something that will be increasingly necessary as the U.S. cannabis industry expands exponentially in the coming decade.